US7379671B2 - Optical transmitter - Google Patents

Optical transmitter Download PDF

Info

Publication number
US7379671B2
US7379671B2 US10/609,366 US60936603A US7379671B2 US 7379671 B2 US7379671 B2 US 7379671B2 US 60936603 A US60936603 A US 60936603A US 7379671 B2 US7379671 B2 US 7379671B2
Authority
US
United States
Prior art keywords
signal
optical
frequency
carrier
suppressed
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related, expires
Application number
US10/609,366
Other languages
English (en)
Other versions
US20040071474A1 (en
Inventor
Kenkichi Shimomura
Takashi Sugihara
Takashi Mizuochi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Electric Corp
Original Assignee
Mitsubishi Electric Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mitsubishi Electric Corp filed Critical Mitsubishi Electric Corp
Assigned to MITSUBISHI DENKI KABUSHIKI KAISHA reassignment MITSUBISHI DENKI KABUSHIKI KAISHA ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: MIZUOCHI, TAKASHI, SHIMOMURA, TAKASHI, SUGIHARA, TAKASHI
Publication of US20040071474A1 publication Critical patent/US20040071474A1/en
Assigned to MITSUBISHI DENKI KABUSHIKI KAISHA reassignment MITSUBISHI DENKI KABUSHIKI KAISHA CORRECTION TO THE SECOND INVENTOR'S NAME Assignors: MIZUOCHI, TAKASHI, SHIMOMURA, KENKICHI, SUGIHARA, TAKASHI
Application granted granted Critical
Publication of US7379671B2 publication Critical patent/US7379671B2/en
Expired - Fee Related legal-status Critical Current
Adjusted expiration legal-status Critical

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/501—Structural aspects
    • H04B10/503—Laser transmitters
    • H04B10/505—Laser transmitters using external modulation
    • H04B10/5051—Laser transmitters using external modulation using a series, i.e. cascade, combination of modulators
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/501—Structural aspects
    • H04B10/503—Laser transmitters
    • H04B10/505—Laser transmitters using external modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/516—Details of coding or modulation
    • H04B10/5165—Carrier suppressed; Single sideband; Double sideband or vestigial
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/516—Details of coding or modulation
    • H04B10/548—Phase or frequency modulation

Definitions

  • the present invention relates to an optical transmitter employed in an optical communications system.
  • intensity modulation is commonly carried out by a simple on-off keying method.
  • An intensity modulator enhances not only the transmission speed of each wavelength but also the capacity of transmission by increasing the number of multiplexed wavelengths.
  • the transmission speed per wavelength has increased to 10 Gbit/s and the number of wavelengths that can multiplexed (hereinafter, “multiplexed wavelengths”) has increased to the tune of a few dozens.
  • the interval between two wavelengths be set greater than 2.5 times the bit rate, in order to avoid spectral overlap of two adjoining optical wavelength signals. Consequently, the frequency usage efficiency that is defined by the ratio of the wavelength interval and the signal frequency is limited to 0.4.
  • the conventional methods of increasing the transmission speed and the number of multiplexed wavelengths to increase the transmission capacity have their demerits.
  • the transmission capacity cannot be improved unless the band of the transmission channel and the optical amplifier are dramatically broadened.
  • FIG. 9 shows the structure of a conventional optical transmitter (See “0.8 bit/s/Hz of Information Spectral Density by Vestigial Sideband Filtering of 42.66 Gb/s NRZ” W. Idler et al., in proceedings of European Conference on Optical communication 2002, 8.1.5.
  • electrical non-return-to-zero (NRZ) signals that are to be transmitted are first converted to plural optical signals by on-off keying modulation process.
  • the optical signals pass through cyclic filters 23 - a and 23 - b where the side band on one side of these optical signals are suppressed to vestigial side band (VSB), thereby narrowing the bandwidth occupied by each optical signal.
  • an optical wave combiner 24 combines these optical signals and outputs them as wavelength-multiplexed signals.
  • a frequency usage efficiency to the tune of 0.8 bit/s/Hz can be achieved by wavelength-multiplexing an optical signal of 42.7 Gbit/s at an interval of 50 GHz, as shown in FIG. 10C .
  • the frequency usage efficiency is defined by obtaining a signal wavelength (40 Gbit/s) after deducting from it an error-correcting redundancy bit.
  • non-return-to-zero on-off keying format that has a relatively narrow bandwidth is used as a modulation format. Consequently, the signal reception sensitivity is low when compared with that of a return-to-zero (RZ) on-off keying format used in a long-distance communications system.
  • RZ return-to-zero
  • the return-to-zero on-off keying format has the advantage of high signal reception sensitivity, due to the high bandwidth of each optical signal, even after their side band is truncated, the bandwidth can still be up to twice that of the non-return-to-zero on-off keying format.
  • the optical transmitter includes an optical modulation processing unit that has a signal carrier-suppressed pulse modulating unit that performs signal carrier-suppressed pulse modulation on a light source signal to thereby create a carrier-suppressed-return-to-zero signal; a phase modulating unit that performs phase modulation on a data signal based on the carrier-suppressed-return-to-zero signal to thereby convert the data signal into a phase-modulated signal; and an optical filtering unit that filters out redundant frequency components included in the phase-modulated signal.
  • the optical transmitter includes an optical modulation processing unit that has a phase modulating unit that performs phase modulation on a data signal to thereby convert the data signal into a phase-modulated signal; a signal carrier-suppressed pulse modulating unit that performs signal carrier-suppressed pulse modulation on the phase-modulated signal to thereby convert the phase-modulated signal into a phase modulated carrier-suppressed-return-to-zero signal; and an optical filtering unit that filters out redundant frequency components included in the phase modulated carrier-suppressed-return-to-zero signal.
  • FIG. 1 is a schematic drawing of the optical transmitter according to a first embodiment of the present invention
  • FIGS. 2A to 2D are explanatory drawings for explaining signal carrier-suppressed pulse modulation in the first embodiment
  • FIG. 3 is a view that shows a frame format of an optical frequency spectrum of an optical modulated signal in the first embodiment
  • FIG. 4 is a view that shows a frame format of an optical frequency spectrum of an optical modulated signal after waveform formation process in the first embodiment
  • FIGS. 5A and 5B are view that show frame formats of wavelength-multiplexed optical signals in the first embodiment
  • FIG. 6 is a view that shows a frame format of an optical signal that is wavelength-multiplexed by conventional methods
  • FIG. 7 is a schematic drawing of the optical transmitter according to a second embodiment of the present invention.
  • FIG. 8 is a schematic drawing of the optical receiver according to a second embodiment of the present invention.
  • FIG. 9 is a schematic drawing of a conventional optical transmitter.
  • FIGS. 10A to 10C are schematic drawing for explaining a conventional wavelength-multiplexing process.
  • FIG. 1 is a schematic drawing of the optical transmitter according to a first embodiment of the present invention.
  • the optical transmitter comprises a plurality of optical modulation processing sections 10 .
  • a laser light source 1 outputs a light source signal of an optical frequency fc.
  • the light source signal enters a Mach-Zender interferometer optical modulator 2 (hereinafter “MZI optical modulator”) that performs signal carrier-suppressed pulse modulation on the entering light source signal and converts it into a carrier-suppressed RZ signal (hereinafter “CS-RZ signal”), based on a clock signal (of a frequency fb/2) that enters from a clock signal source 5 .
  • MZI optical modulator Mach-Zender interferometer optical modulator 2
  • CS-RZ signal carrier-suppressed RZ signal
  • An optical phase modulator 3 performs, based on the CS-RZ signal, phase modulation on a data signal (signal frequency fb) output from a data signal source 6 .
  • An optical filter 4 performs waveform creation on the phase-modulated data signal and creates an optical output signal.
  • An optical wave combiner 7 wavelength-multiplexes a plurality of such optical output signals output from each of the plural optical modulation processing sections 10 and outputs the wavelength-multiplexed signal to a transmission channel.
  • optical modulation processing units 10 The function of all the optical modulation processing units 10 is the same. Hence, in the following description, the functioning of only one optical modulation processing unit 10 is described.
  • the laser light source 1 generates a light source signal of a carrier frequency fc.
  • the MZI optical modulator 2 may, for instance, be made of lithium niobate and may carry out a signal carrier-suppressed pulse modulation process by the method disclosed in, for instance, “320 Gbit/s (8 ⁇ 40 Gbit/s) WDM transmission over 367-km zero-dispersion-flattened line with 120-km repeater spacing using carrier-suppressed return-to-zero pulse format”, Yutaka, Miyamaoto, et al., in postdeadline papers of Optical Amplifiers and Their Applications Topical Meeting, Jun. 11, 1999.
  • FIG. 2A to FIG. 2D are explanatory drawings that show the signal carrier-suppressed pulse modulation process carried out by the MZI optical modulator 2 .
  • FIG. 2A shows modulation characteristics of the MZI optical modulator 2 .
  • the MZI optical modulator 2 outputs a light signal of an intensity that is in accordance with the voltage applied to the clock signal.
  • the MZI optical modulator 2 modulates the light source signal fc by considering the clock signal as the applied voltage. After modulation the optical output signal appears as a CS-RZ signal that has an alternating phase, viz., 0, ⁇ , 0, ⁇ , . . . and so on.
  • the clock signal (with a frequency of fb/2), at peak voltages a to d is modulated to a CS-RZ signal (see FIG. 2C ) and is output at a frequency fb and with an alternating signal phase as 0, ⁇ , 0, ⁇ , . . . for the peak voltages a, b, c, and d, respectively.
  • the optical frequency spectrum (see FIG. 2D ) of the CS-RZ signal depending on the influence by the alternating signal phases 0 and ⁇ , will have two carrier frequencies, namely, fc ⁇ fb/2 and fc+fb/2.
  • the frequency component fc of the light source signal is suppressed in the mutual offsetting of alternating signal phase components.
  • the optical phase modulator 3 inputs the data signal (with a signal frequency of fb) output from the data signal source 6 and performs optical phase modulation on the CS-RZ signal and converts it into a light source signal.
  • the data signals 0 and 1 are converted to optical modulated signals with an optical phase of 0 and ⁇ , respectively.
  • FIG. 3 is a view that shows a frame format of an optical frequency spectrum of the optical modulated signal.
  • the two carrier frequency components (fc ⁇ fb/2 and fc+fb/2) of the CS-RZ signal are separately phase modulated. Consequently, the optical modulated signal output from the optical phase modulator 3 is made of two superimposed frequency spectrums that are offset by the central frequency fb.
  • the two frequency spectrums contain'the same information signal components in the frequency bands below fc ⁇ fb/2 and above fc+fb/2, thereby loading the optical modulated signal with redundant frequency components.
  • FIG. 4 is a view that shows a frame format of an optical frequency spectrum of the optical modulated signal after waveform formation process.
  • the optical filter 4 extracts only those frequency components that fall within the range of fc ⁇ fb/2 to fc+fb/2, suppresses all frequency components that are below fc ⁇ fb/2 and above fc+fb/2, and creates an optical output signal after waveform formation process. As a result, the bandwidth of the optical output signal is limited to fb.
  • pluraliturality of optical output signals output from plural optical modulation processing sections 10 are multiplexed in the optical wave combiner 7 and output to the transmission channel.
  • FIG. 5A is a view that shows a frame format of an optical frequency spectrum of an optical signal that is wavelength-multiplexed in the first embodiment.
  • Each multiplexed optical output signal is confined to the frequency bandwidth fb. Therefore, even if a plurality of optical output signals are placed at a frequency interval fb, the spectrum of the optical output signals do not overlap. Consequently, the optical receiver receives each of the multiplexed optical output signals distinctly.
  • the frequency usage efficiency in such an optical transmitter can logically be enhanced by up to 1.0 bit/s/Hz.
  • FIG. 5B is a view that shows a frame format of an eye pattern of the wavelength-multiplexed optical signal. Though the clear portions of the eye pattern are narrow due to suppression of redundant frequency components, the demodulation process that is carried out in the optical receiver widens the eye pattern openings (clear portions) sufficiently.
  • FIG. 6 is a view that shows a frame format of an optical spectrum of an optical signal that is wavelength-multiplexed without removing the redundant frequency components, as in conventional optical transmitters.
  • the frequency bandwidth of each of the optical output signals is wider than fb, the spectrums of the plurality of optical output signals, placed at a frequency interval fb, overlap and are not distinctly received in the optical receiver.
  • the data signal is modulated according to the CS-RZ signal created by the MZI optical modulator.
  • the frequency bandwidth of the modulated signal is narrowed in order to facilitate wavelength multiplexing. Consequently, the frequency usage efficiency is enhanced without compromising on the signal reception sensitivity.
  • an optical phase modulator is used for carrying out phase modulation of the data signal.
  • a lithium niobate MZI optical modulator may also be used for phase modulating the data signal.
  • arrayed waveguide grating may be used as the optical filter 4 .
  • the CS-RZ signal output from the MZI optical modulator 2 is passed into the optical phase modulator 3 to phase modulate the data signal.
  • the structure need not be limited to this and can be made such that after phase modulation of the data signal according to the light source signal from a laser light source, the modulated data signal is carrier-suppressed-pulse-modulated by the MZI optical modulator and passed through the optical filter to create a waveform.
  • the optical phase modulator 3 phase modulates the data signal according to the CS-RZ signal.
  • the optical transmitter includes a differential coder that performs differential coding to the data signal.
  • the optical phase modulator 3 performs phase modulation on the differential-coded data signal according to the CS-RZ signal.
  • a data signal output from a data signal source 6 undergoes differential-coding by a differential coder 11 .
  • the differential-coded data signal enters an optical phase modulator 3 and is phase modulated according to a separately generated CS-RZ signal.
  • the optical modulated signal passes through an optical filter that suppresses the redundant frequency components, and is subsequently multiplexed by an optical wave combiner 7 , and transmitted to a transmission channel.
  • the optical receiver according to the second embodiment may, for instance, have the configuration disclosed in ‘Optical Receiver Module for bit synchronous strong modulation DPSK-DD transmission system using PLC platform (Yamada et al., The Institute of Electronics, Information and Communication Engineers, Electronic Society Meeting papers, C-3-111, P237, 2000)’ and performs delayed demodulation on the optical signal received from the optical transmitter.
  • FIG. 8 is a schematic drawing of an optical receiver of the optical communications system according to a second embodiment of the present invention.
  • an optical interferometer 13 creates an interference signal of an optical receiver signal 12 and a 1-bit time delay.
  • a differential optical/electrical converter 14 converts the interference signal into a demodulated signal 15 , which is an electrical signal.
  • the optical interferometer 13 then combines the distributed components of the optical receiver signal 12 output from the two arms A and B and makes them undergo optical interference. As a result, when the phase of both distributed components are the same (0-0, ⁇ - ⁇ ), demodulated pulse is output from port A, and when the phases of the two distributed components are reversed (0- ⁇ , 0- ⁇ ), demodulated pulse is output from port B in FIG. 8 .
  • the differential optical/electrical converter 14 converts the demodulated pulse output from port A and port B into electrical signals using an optical diode, calculates the difference between the two electrical signals, and outputs as a demodulated signal.
  • the frequency usage efficiency of the multiplexed optical signals can be enhanced.
  • the optical transmitter performs differential-coding on the data to be transmitted and the optical receiver performs delayed demodulation on the optical reception signal. Consequently, the structure of the optical receiver can be simplified to a great extent.
  • a data signal is modulated according to a CS-RZ signal generated by signal carrier-suppressed pulse modulation process.
  • the modulated data signal then passes through an optical filter where the bandwidth of the signal is confined.
  • a data signal is phase modulated and made to undergo signal carrier-suppressed pulse modulation and subsequently passed through an optical filter to confine its bandwidth.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Optics & Photonics (AREA)
  • Optical Communication System (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
US10/609,366 2002-10-11 2003-07-01 Optical transmitter Expired - Fee Related US7379671B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2002298727A JP4110913B2 (ja) 2002-10-11 2002-10-11 光送信器
JP2002-298727 2002-10-11

Publications (2)

Publication Number Publication Date
US20040071474A1 US20040071474A1 (en) 2004-04-15
US7379671B2 true US7379671B2 (en) 2008-05-27

Family

ID=32025586

Family Applications (1)

Application Number Title Priority Date Filing Date
US10/609,366 Expired - Fee Related US7379671B2 (en) 2002-10-11 2003-07-01 Optical transmitter

Country Status (4)

Country Link
US (1) US7379671B2 (ja)
EP (1) EP1408631B1 (ja)
JP (1) JP4110913B2 (ja)
DE (1) DE60324649D1 (ja)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090097867A1 (en) * 2005-10-31 2009-04-16 Mikio Yoneyama Optical receiver using mach-zehnder interferometer
US8897654B1 (en) * 2012-06-20 2014-11-25 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration System and method for generating a frequency modulated linear laser waveform

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100617709B1 (ko) 2004-08-05 2006-08-28 삼성전자주식회사 주파수 변조 방식의 광송신 장치 및 방법
US8073342B2 (en) * 2007-05-04 2011-12-06 Massachusetts Institute Of Technology Method and apparatus for transmitting optical signals
US20090252502A1 (en) * 2008-04-07 2009-10-08 Futurewei Technologies, Inc. Methods and systems for optical communication
JP2014106492A (ja) * 2012-11-29 2014-06-09 Fujitsu Ltd 光信号処理装置及び光信号処理方法

Citations (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5228043A (en) * 1990-07-18 1993-07-13 Fujitsu Limited Direct modulation phase shift keying (dm-psk) transmission system
US5305134A (en) * 1989-08-30 1994-04-19 Hitachi, Ltd. Optical frequency division multiplexing transmitter and optical frequency division multiplexing transmission apparatus
JPH09236781A (ja) 1996-02-28 1997-09-09 Nippon Telegr & Teleph Corp <Ntt> 光送信装置およびそれを用いた光伝送システム
EP0977382A2 (en) 1998-07-29 2000-02-02 Nippon Telegraph and Telephone Corporation Optical transmission system
US6072615A (en) 1997-06-13 2000-06-06 Lucent Technologies Inc. Phase modulator-based generation of high-quality high bit rate return-to-zero optical data streams
JP2001308792A (ja) 2000-04-26 2001-11-02 Nippon Telegr & Teleph Corp <Ntt> 光通信装置、光送信器および光受信器
US20020021464A1 (en) * 2000-08-04 2002-02-21 Way David G. Tunable channel spacing for wavelength division multiplexing (WDM) transport system
JP2002164850A (ja) 2000-09-14 2002-06-07 Nec Corp 光送信器及び光変調方法
US20020131134A1 (en) * 2001-03-16 2002-09-19 Hait John N. Hyper-dense photonic signal method
JP2002281095A (ja) 2001-03-15 2002-09-27 Mitsubishi Electric Corp 多重装置
US6459519B1 (en) * 1997-04-09 2002-10-01 Matsushita Electric Industrial Co., Ltd. Optical transmitter-receiver
EP1298819A2 (en) 2001-09-26 2003-04-02 Kabushiki Kaisha Toshiba Apparatus and method for optical modulation
US6650846B1 (en) * 1998-06-09 2003-11-18 Nec Corporation Optical transmitter and optical transmission system
US20030219259A1 (en) * 2002-04-15 2003-11-27 Jonas Martensson Phase modulation for an optical transmission system
JP2004104385A (ja) 2002-09-09 2004-04-02 Kddi Submarine Cable Systems Inc 光伝送システム、光送信装置及びこれらの方法

Patent Citations (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5305134A (en) * 1989-08-30 1994-04-19 Hitachi, Ltd. Optical frequency division multiplexing transmitter and optical frequency division multiplexing transmission apparatus
US5228043A (en) * 1990-07-18 1993-07-13 Fujitsu Limited Direct modulation phase shift keying (dm-psk) transmission system
JPH09236781A (ja) 1996-02-28 1997-09-09 Nippon Telegr & Teleph Corp <Ntt> 光送信装置およびそれを用いた光伝送システム
US6459519B1 (en) * 1997-04-09 2002-10-01 Matsushita Electric Industrial Co., Ltd. Optical transmitter-receiver
US6072615A (en) 1997-06-13 2000-06-06 Lucent Technologies Inc. Phase modulator-based generation of high-quality high bit rate return-to-zero optical data streams
US6650846B1 (en) * 1998-06-09 2003-11-18 Nec Corporation Optical transmitter and optical transmission system
EP0977382A2 (en) 1998-07-29 2000-02-02 Nippon Telegraph and Telephone Corporation Optical transmission system
JP2001308792A (ja) 2000-04-26 2001-11-02 Nippon Telegr & Teleph Corp <Ntt> 光通信装置、光送信器および光受信器
US20020021464A1 (en) * 2000-08-04 2002-02-21 Way David G. Tunable channel spacing for wavelength division multiplexing (WDM) transport system
JP2002164850A (ja) 2000-09-14 2002-06-07 Nec Corp 光送信器及び光変調方法
JP2002281095A (ja) 2001-03-15 2002-09-27 Mitsubishi Electric Corp 多重装置
US20020131134A1 (en) * 2001-03-16 2002-09-19 Hait John N. Hyper-dense photonic signal method
EP1298819A2 (en) 2001-09-26 2003-04-02 Kabushiki Kaisha Toshiba Apparatus and method for optical modulation
US20030219259A1 (en) * 2002-04-15 2003-11-27 Jonas Martensson Phase modulation for an optical transmission system
JP2004104385A (ja) 2002-09-09 2004-04-02 Kddi Submarine Cable Systems Inc 光伝送システム、光送信装置及びこれらの方法

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
Idler et al., 0.8bit/s/Hz of Information Spectral Density by Vestigial Sideband Filtering of 42.66 Gb/s NRZ, Sep. 8, 2002.
Miyamoto Y et al.: "Duobinary carrier-suppressed return-to-zero formal and its application to 100GHz-spaced 8x43 Gbit/s DWDM unrepeatered transmission over 163 km" Optical Fiber Communication Conference. (OFC). Technical Digest Postconference Edition. Anaheim, CA, Mar. 17-22, 2001, Trends in Optics and Photonics Series. Tops. vol. 54, Washington, WA : OSA, US, vol. 2, Mar. 17, 2001, pp. TuU4-1, XP010545838 ISBN: 1-55752-655-9.
Morita et al., 100% Spectral-Efficient 25x42.7 GBIT/S Transmission Using Asymmetrically Filtered CS-RZ Signal and a Novel Crosstalk Suppressor, KDDI R&D Laboratories Inc. Japan, Post-deadline session 4: PD4.7, Sep. 8, 2002.

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090097867A1 (en) * 2005-10-31 2009-04-16 Mikio Yoneyama Optical receiver using mach-zehnder interferometer
US7995930B2 (en) * 2005-10-31 2011-08-09 Ntt Electronics Corporation Optical receiver using Mach-Zehnder interferometer
US8897654B1 (en) * 2012-06-20 2014-11-25 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration System and method for generating a frequency modulated linear laser waveform
US20150104193A1 (en) * 2012-06-20 2015-04-16 U.S.A. As Represented By The Administrator Of The National Aeronautics And Space Administration System and Method for Generating A Frequency Modulated Linear Laser Waveform
US9712250B2 (en) * 2012-06-20 2017-07-18 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration System and method for generating a frequency modulated linear laser waveform

Also Published As

Publication number Publication date
JP2004135139A (ja) 2004-04-30
EP1408631A2 (en) 2004-04-14
JP4110913B2 (ja) 2008-07-02
EP1408631A3 (en) 2005-12-14
EP1408631B1 (en) 2008-11-12
DE60324649D1 (de) 2008-12-24
US20040071474A1 (en) 2004-04-15

Similar Documents

Publication Publication Date Title
EP1271808B1 (en) Optical transmitter and optical transmission system
US7340182B2 (en) Multiplexer
US20060013596A1 (en) Bandwidth limited frequency shift keying modulation format
US8577224B2 (en) Optical shaping for amplification in a semiconductor optical amplifier
JP5068240B2 (ja) 光伝送方式、送信器及び受信器
US6496297B1 (en) Device and method for modulating an optical signal
US8687970B2 (en) Modulator and demodulator for a differential optical modulation format with eight phase changes
KR100539893B1 (ko) 고밀도 파장분할다중화방식 광전송 시스템을 위한 광 송신기
EP1524783A2 (en) RZ-AMI optical transmitter module
EP1526664B1 (en) Optical phase modulation
EP1633061B1 (en) Method and system for increasing the spectral efficiency of binary coded digital signals
EP1424795B1 (en) Optical transmission system using optical phase modulator
US7379671B2 (en) Optical transmitter
EP3497825B1 (en) Encoding for optical transmission
US6430336B1 (en) Device and method for minimizing optical channel drift
JP5507341B2 (ja) 光符号分割多重用送信回路及び光符号分割多重用受信回路
US20040208583A1 (en) Single sideband dense wavelength division multiplexed optical transmission scheme
US6407837B1 (en) Use of bandwidth efficient modulation techniques in a wavelength division multiplexed optical link
JP2004235988A (ja) 光送信器、光受信器、光伝送システムおよび光伝送方法
JP4493439B2 (ja) 光通信方法
JP3761528B2 (ja) 光送信装置および光送信方法

Legal Events

Date Code Title Description
AS Assignment

Owner name: MITSUBISHI DENKI KABUSHIKI KAISHA, JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SHIMOMURA, TAKASHI;SUGIHARA, TAKASHI;MIZUOCHI, TAKASHI;REEL/FRAME:014257/0127

Effective date: 20030616

AS Assignment

Owner name: MITSUBISHI DENKI KABUSHIKI KAISHA, JAPAN

Free format text: CORRECTION TO THE SECOND INVENTOR'S NAME;ASSIGNORS:SHIMOMURA, KENKICHI;SUGIHARA, TAKASHI;MIZUOCHI, TAKASHI;REEL/FRAME:016786/0315

Effective date: 20030616

FEPP Fee payment procedure

Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

FPAY Fee payment

Year of fee payment: 4

REMI Maintenance fee reminder mailed
LAPS Lapse for failure to pay maintenance fees
STCH Information on status: patent discontinuation

Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362

FP Lapsed due to failure to pay maintenance fee

Effective date: 20160527